Feasibility of N-methylpyrrolidone (NMP) as an electron donor for denitrification

Abstract:

[Objective] N-methylpyrrolidone (NMP) was used as an electron donor for denitrification to treat wastewater. [Methods] NMP and glucose as electron donors were respectively added into the simulated effluent from wastewater treatment plant for denitrification, during which they were compared for the removal of nitrates. The fate of nitrogen released during the denitrification was studied, and the released nitrogen was further treated. Furthermore, we submitted the sludge samples acclimated with NMP and glucose for high-throughput sequencing to investigate their mechanisms of denitrification. [Results] The NMP-acclimating sludge showed the nitrate-N removal rate 67% higher than the glucose-acclimating sludge. After 8 h of denitrification with NMP as the electron donor, the total nitrogen (TN) composed of residual nitrate N, generated nitrite N, and released ammonium N from NMP biodegradation was similar to the TN after the denitrification with glucose as the electron donor. [Conclusion] The wastewater containing NMP could be used as the electron donor for deep nitrate removal, although it was directly treated as the wastewater before. High-throughput sequencing indicated that NMP was different from glucose in the mechanism of denitrification when being used as the electron donor. As one of the nitrogen-containing heterocyclic compounds, NMP releases the electron donor for denitrification through the biodegradation of organic acids after the cleavage of NMP ring. However, glucose releases its electron donor for denitrification through the biodegradation without ring cleavage because of its simple structure. The results have theoretical significance for utilizing nitrogen-containing heterocyclic compounds as electron donors for denitrification.